Technical Field
The present invention relates to a catalyst for synthesizing multi-wall carbon nanotubes, and in particular to a catalyst for synthesizing multi-wall carbon nanotubes, a method for producing the catalyst, and multi-wall carbon nanotubes synthesized by the catalyst, which are able to allow an easier distribution of synthesized multi-wall carbon nanotubes and significantly improve conductivity.
Background Art
The carbon nanotube (CNT) is a kind of a carbon allotrope formed in a cylindrical tube structure wherein carbons are coupled into a hexagonal configuration. Since the CNT, in general, is formed in a tube shape the diameter of which is a couple of nm, it is called a nanotube. This nanotube is hollow and light and has a tensile strength which is 100 times, to the maximum, of a steel which has the same thickness as the nanotube and has a physical property which allows the CNT to bend 90°. For this reason, the CNT is receiving attention as a new material. Moreover, it has a high heat and electrical conductivity and provides the characteristics of a conductor and a semiconductor which are determined based on the angle where carbon layers are wound. Furthermore, the carbon nanotube may be classified into a single walled carbon nanotube (SWNT) and a multi-walled carbon nanotube (MWNT).
The carbon nanotube, in general, may be produced by any of an electric discharge method, a laser deposition method, a plasma chemical vapor deposition method, a thermochemical deposition method, a vapor synthesis method, an electrolysis method, etc., among which the aforementioned vapor synthesis method is receiving the biggest attention since the deposit of a carbon nanotube can be formed in such a way to directly supply a gas containing carbons, and a catalyst metal into a reaction furnace and react them without using any substrate, and the carbon nanotubes can be mass-produced, while providing a high economic efficiency. In the aforementioned vapor synthesis method, the use of a catalyst metal is essential, and Ni, Co or Fe is most used as a catalyst metal. Each catalyst metal particle may function as one seed to form a carbon nanotube.
Meanwhile, as a prior art document which describes a carbon nanotube and a catalyst for producing the same, there are the Korean patent laid-open No. 2010/0042765 entitled “a loading catalyst for a carbon nanotube synthesis, a method for producing the same, and a carbon nanotube using the same”, and the Korean patent laid-open No. 2012/0093458 entitled “a high conductive carbon nanotube having a vertical orientation bundle structure and a high conductive polymer nano-composite composition using the same”, both of which disclose a crushed spherical catalyst and a sheet type catalyst, but they still have a problem since it is impossible to economically mass-produce a high quality carbon nanotube having the natural good characteristics of the carbon nanotubes.
More specifically, the specific surface area of the catalyst is not wide, so the production amount of the carbon nanotubes are not lots as compared to the used amount of the catalyst, and the surface area of the produced carbon nanotube is not wide, and the quality is not even. For these reasons, the aforementioned carbon nanotubes are not good to be used for the sake of various potential applications wherein the natural good characteristics of the carbon nanotubes can be revealed.